After maintenance work, in particular after repairs, aircraft engines have to be tested in a test run. This produces a considerable amount of noise which has to be shielded, in particular if said test run includes operating the engines at full load.
In the case of a known noise insulation device of the type mentioned at the beginning (WO 98/06625), the aircraft is brought backwards into a noise insulation hangar. The hangar, which is generally entirely covered by a roof, has to have a considerable height in order to be able to accommodate the rudder unit, or a slot for the rudder unit has to be provided in the roof and then has to be closed after the aircraft is brought into the noise insulation hangar. The opening into which the aircraft is brought is then closed by doors which have conducting surfaces which damp the sound emerging to the front and also deflect the inflowing air in such a manner that it flows approximately in the longitudinal direction of the aircraft into the engines.
This previously known noise insulation hangar may indeed be designed highly effectively, as far as the damping of the outwardly penetrating noise is concerned. However, its construction is associated with high costs. This is because the roof has to cover large distances between the side walls over the entire length of the aircraft in a self-supporting manner, which, with the large wing spans of modern large-capacity aircraft, makes very expensive and complicated roof constructions necessary. Also, the heavy, door-like elements which support the conducting surfaces have to be able to be opened in order for the aircraft to be rolled in. This not only requires complicated rolling and driving systems. What is more, since the conducting surfaces are self-supporting, they also have to be of highly stable design. A further disadvantage is that the previously known noise insulation hangar cannot be expanded.